GOOLOO GT4000S 4000A 12V Jump Starter

A 4,000 amp pack built around a 100 watt USB-C port

The GT4000S is a 12-volt lithium polymer jump starter that the manual rates at 4,000 amps peak with a starting current of 800 amps. The listing claims it will turn over gasoline engines up to 12 litres and diesel engines up to 10 litres; no GOOLOO document we read states an engine rating for this model.

Its USB-C port works in both directions at PD 100 watts maximum, stepping through 5, 9, 12 and 15 volts at 3 amps and 20 volts at 5 amps, with backwards compatibility noted. Alongside it the manual lists a QC3.0 USB output at 18 watts maximum and a second USB output at 5 volts and 2.4 amps.

The manual gives a full charge time of about 1.2 hours when a quick-speed PD 100 watt wall charger is used. Note the wording: the package content in that same manual includes a 100 watt car charger, not a wall charger, so the headline charging time assumes something you may have to supply.

The DC socket is an output, and the manual says so plainly

The manual specifies the DC output as 15 volts at 10 amps, 150 watts maximum. The listing points at tyre inflators and inverters as the things it is for, and a cigarette lighter socket adapter is in the manual's package list, so ordinary 12-volt car accessories can plug in.

The manual adds one line that is easy to miss: the DC port is an output port used to power car products and is not a charging port. Do not try to refill the pack through it.

Recharging goes through the USB-C port instead, which is also how the 100-watt laptop charging claim works. The listing is specific that laptop-speed charging is on the Type-C port only.

Capacity and current are printed differently in each document

The listing's title and capacity field both say 20,000 milliamp hours. The manual's technical specification says 74 watt hours, which it writes as 5,000 milliamp hours at 14.8 volts. Neither document mentions the other figure, so ask the seller which applies to the unit shipping now.

Current is inconsistent too. Both documents agree the peak is 4,000 amps, but the manual gives a starting current of 800 amps while the listing's amperage field says 1,000 amps. Nothing in either document reconciles the two, and they are separate rows rather than two names for one figure.

Cycle life is over 1,000 cycles in the manual, and the operating range is minus 20 to 60 degrees Celsius, which is minus 4 to 140 Fahrenheit. The manual's specification block publishes no size and no weight; the listing's 9.05 by 3.93 by 2.12 inches and 4.24 pounds are the only figures we found.

Claims that appear only in the seller's copy

Three of the listing's selling points have no counterpart in the maker document we read. It says a single full charge is good for 60 jump starts, that a five-minute charge is enough to start a car, and that the pack has a 24-month stand-by time so regular charging is not necessary.

None of those three appears in the manual's specification, package or warranty pages. That does not make them false, but it does mean they are unverified by the document that ships with the product, so treat them as marketing rather than as rated figures.

The same applies to the 3.2-inch LED screen and the 400-lumen flashlight with SOS, spotlight and strobe modes: those come from the listing. The manual we read does not publish a brightness figure or a screen size.

What the box contains according to the maker

The manual's package list is unusually full for this category: the host unit, a carrying bag, a USB-A to USB-C cable, a USB-C to USB-C cable, the jumper cable, an SC 100-watt maximum car charger, a cigarette lighter socket adapter and the user manual.

That means the accessory you need for the DC output is listed as included rather than as an extra purchase. Check the delivered contents against the manual's list rather than against a bullet, because the two are not written the same way.

Because there is no wall charger in that list, decide in advance whether you want a PD 100-watt wall unit for the 1.2-hour figure, or whether charging from the car with the supplied charger is good enough for how you plan to use it.

Eighteen months, claimed with an order number

The manual sets out three things: 18 months of online after-sales service, a 30-day money-back window it says is applied for through Amazon, and replacement of a unit that fails from a manufacturing issue at any point inside the 18 months.

The disclaimer that follows is where the limits sit. The original purchaser must show the original receipt or order number for the warranty to take effect, and coverage excludes normal wear and tear, physical abuse, improper installation, misuse, modification and unauthorized third-party repairs.

GOOLOO also states it is not responsible for accidental or indirect damage from incorrect use, and that every claim is limited to repair or replacement at its sole discretion. Support is listed as separate email addresses for the United States and Europe plus a toll-free line staffed weekdays on Pacific time, with technical service described as lifetime even though the warranty runs 18 months.

One identity note belongs on this page rather than in a footnote. The manual's cover carries model number JS-271 alongside the GT4000S name, and the Amazon listings for two other GOOLOO packs, the GT4000 Arctic and the GT6000, carry that same JS-271 in their part-number fields. No GOOLOO document we read explains why one part number covers several models, so quote the GT4000S name and this ASIN when contacting support rather than the part number alone.